The present invention relates to a device for receiving/transmitting electromagnetic waves with omnidirectional radiation of the antenna-type which can be used most particularly in the field of wireless transmissions.
In the case of domestic networks using wireless transmissions, the antenna design must comply with particular requirements which especially result from the topology of the environment. Thus in this type of application, as shown in FIG. 1, communicating devices which may be located at any point in the same room, in different rooms or even on different floors or levels must be considered. For example, FIG. 1 shows a house with four rooms, three 1, 1xe2x80x2, 1xe2x80x3 of which have communicating equipment. Room 1 has a decoder 2 connected to a television set 3, the decoder being connected to an antenna 4 communicating with a satellite 5. Moreover, the decoder 2/television set 3 assembly is fitted with an antenna 6 belonging to a wireless network capable of communicating via an antenna 9 with a computer 7 and a CD ROM reader 8 placed in another room 1xe2x80x2. These assemblies must also be able to communicate with another television set 10 positioned in a room 1xe2x80x3 on a lower floor. Under these conditions, and so as to ensure complete coverage of the communication space for the purpose of connecting all the terminals of the network, it would appear necessary to design antennas having omnidirectional radiation.
At present, the antennas most commonly used to meet the requirements for omnidirectional radiation consist of dipole antennas or antennas of the patch type.
A dipole antenna referenced 20 enables azimuthal omnidirectional coverage to be obtained, as shown in FIG. 2, however it has a hole in the axis defined by the radiating element. Consequently, although the dipole antenna is able to communicate with the telephone 21 and the television set 22 located on the same floor, connection with the computer 23 located on an upper floor is not guaranteed.
With regard to the printed antennas of the patch type, as shown in FIG. 3, they comprise schematically a substrate 30 on which a printed patch 31 is produced. As a result, the patch antenna has hemispherical radiation 32, which limits the coverage to the upper half-space of the earth plane 30.
To overcome the coverage problem, several antenna topologies have been proposed. However, they all lead to three-dimensional configurations in which the printed antennas are produced on supports of any shape. Now, these solutions are still bulky and their manufacture tricky for mass production.
The aim of the present invention is therefore to overcome the above drawbacks by proposing a new antenna topology guaranteeing, on the one hand, overall coverage of space and, on the other hand, limited bulk. This new topology is based on a type of printed antennas such as the Vivaldi antennas, proposed in French Patent Application No. 98-13855 filed in the name of the applicant. The antenna proposed in the aforementioned patent application consists of a coplanar circular arrangement, about a central point, of Vivaldi-type printed radiating elements, making it possible to present several directional beams sequentially over time, the set of beams giving complete 360xc2x0 coverage of space. Improvements have been made to this type of antennas, in particular, in French Patent Application No. 00-15715 filed in the name of the applicant. In that application, an embodiment allowing an operating mode which is no longer sequential but simultaneous was proposed, that is to say that the set of beams operate at the same time, so as to generate omnidirectional radiation in contrast with the directional radiation of the embodiment described in the previous application. However, the pattern of the structure thus excited has areas of zero field in an angular sector surrounding the directions orthogonal to the plane of the substrate, this sector being called a blind zone. These blind zones are defined by the aperture in the H plane of the radiation pattern of an elementary xe2x80x9cVivaldixe2x80x9d antenna.
The aim of the present invention is therefore to propose an improvement to the structure described above, which makes it possible to eliminate the areas of zero field described above.
Consequently, the subject of the present invention is a device for receiving/transmitting electromagnetic waves with omnidirectional radiation of the antenna type comprising a first set of means for receiving/transmitting waves with longitudinal radiation of the printed antenna type, the said means being arranged in order to receive a wide azimuthal sector, characterized in that it further comprises at least a second means for receiving/transmitting waves with transverse radiation of the printed antenna type, the second means having radiation complementary to the radiation of the first means, and means capable of connecting in emission the said first and second wave receiving/transmitting means.
According to a preferred embodiment, the means capable of connecting in emission the first set of means for receiving/transmitting waves with longitudinal radiation and the second means for receiving/transmitting waves with transverse radiation consist of a common feed line produced by printed technology. This common feed line is formed by a microstrip line or a coplanar line crossing all the slots of the printed slot antennas constituting the first receiving/transmitting set and the second receiving/transmitting means of the slot type, the length of the line between two slots of the first set being equal at the central operating frequency of the system to kxcexm, the length of the line between the last slot of the first set and the slot of the second receiving/transmitting means being equal at the central operating frequency of the system to kxcexm/2 and the length of the line between one end of the line and the slot of the second receiving/transmitting means being equal to kxe2x80x2xcexm/4 where xcexm=xcex0/xcex5reff where xcex0 is the wavelength in vacuo, xcex5reff is the equivalent permittivity of the line, and k and kxe2x80x2 are integers. When the second transmitting/receiving means of the slot type consists of a patch, the feed line is directly connected to the patch without additional length.
Furthermore, each means for receiving/transmitting waves with longitudinal radiation of the printed antenna type consists of a printed slot antenna of the Vivaldi antenna or Yagi antenna type, the antennas hereinabove being arranged at regular intervals around a single point and coplanar so as to be able to radiate over a 360xc2x0 angle sector.
Similarly, the second means for receiving/transmitting waves with transverse radiation of the printed type consists of a slot which is symmetrical with respect to a point or an antenna of the patch type where only a connection to the upper or lower floor is necessary. This slot or this patch is circular or square. Thus, according to one characteristic of the invention, the first set of means for receiving/transmitting waves with longitudinal radiation and the second means for receiving/transmitting waves with transverse radiation are produced on the same substrate so as to be symmetric about the same point.